The present invention relates to an apparatus for counting flexible flat objects arranged in an overlapping formation, in particular printed products.
An apparatus of this type is disclosed by EP-A-0 408 490. A conveying device which is driven at conveying speed in the conveying direction and constructed as a belt conveyor is intended to convey objects in an overlapping formation, in which each object rests on the preceding one, in a system cycle rate. Arranged underneath the conveying device is a counting device, having a guide means which extends in the conveying direction and on which a slide is freely displaceably mounted. The slide can be moved to and fro, in and counter to the conveying direction, coordinated with the system cycle rate by means of a drive, the speed in the conveying direction, at least in one section of the guide means, being higher than the conveying speed, in order to bring a contact element arranged on the slide into contact with the rear edge of the object respectively moved past the counting device. The relative movement between the object and the slide causes the contact element to move out of the conveying area and, as a result, to activate a sensor element in order to emit a signal to a counter. In order to avoid the contact element exerting any influence on the position of the relevant object in any case, a pressure element is provided which presses the objects against the conveyor belt so that they are carried along firmly. In order to permit the counting of objects which are conveyed at irregular time intervals, coarse detection of the objects is performed and, accordingly, the contact element is activated at irregular time intervals.
It is an object of the present invention to provide a generic apparatus which, with a simple construction, ensures precise counting even of objects which occur at irregular intervals.
The above and other objects and advantages of the present invention are achieved by the provision of a conveying device which is driven at a conveying speed in a conveying direction and which is intended to convey the objects. A counting device includes a contact element and a sensor element mounted for movement along a guide which extends in the conveying direction, and a drive is provided for moving the elements along the guide at a higher speed than the conveying speed so as to bring the contact element into engagement with a rear region of each object conveyed past the counting device. The contact element then is deflected into engagement with the sensor element which emits a signal to a counter.
The object in each case interacting with a contact element is displaced in the conveying direction by means of a catch element driven together with the contact element. As a result, each object, even if the objects occur in an irregular overlapping formation, can interact only once with the contact element, which leads to extremely precise counting in a very simple way. The movement of the contact and catch element therefore does not need to be coordinated with a system cycle rate, the only condition is that the frequency with which these elements are moved cyclically in the conveying direction is at least as high as the maximum frequency with which the objects can occur. Even counting printed products with a prefold does not present any problems. The information about the time and the location at the end of the displacement by means of the catch element also means that the precise position of the object on the conveying device is known, which may be important for further processing. The apparatus is most suitable to process overlapping formations, in which the objects in each case rest on the preceding or in each case on the following object.